1. Field of the Invention
The present invention is related to an axle assembly for branching the driving power transmitted from an engine to right and left driving axles.
2. Related Art
Hitherto, various types of axle assemblies for branching the driving power of the engine to a pair of right and left driving axles have been proposed. Among those assemblies, Japanese Utility Model Application Laid-open No. Sho-57-128524 discloses an axle assembly of the type that includes an axle case with an opening formed therein through which a differential gear device is inserted, and a lid for covering the opening, which lid acting as a support for supporting thereon the differential gear device and an input shaft for transmitting the driving power of the engine to the differential gear device.
The differential gear device in the above axle assembly includes a differential cage for accommodating a pair of side gears and a bevel gear meshed with the pair of side gears, and a ring gear relatively non-rotatably connected with the differential cage, in which the differential cage is supported on the lid.
The axle assembly having the above arrangement enables the differential gear device to be accommodated within the axle case while being supported by the lid, thereby contributing to efficient assembly.
However, since the aforesaid conventional axle assembly is designed to have the differential cage encompassed by the ring gear, it necessitates the axle assembly to have a maximum diameter larger than the differential case. That is, this conventional axle assembly has a maximum diameter necessarily defined by the ring gear designed to encompass the differential cage, so that the axle case for accommodating the axle assembly must have an enlarged inner diameter.
The diametrical enlargement of the axle case goes against an ultimate goal of reduction in size of a vehicle, as well as invites not only increased manufacturing cost but also shortened distance between the axle case and a road surface under the running vehicle. Also, such shortened distance sometimes poses a problem of causing accidental contacts between the axle case and stones or any other matters on the road surface.
To address the above problems, it is an object of the present invention to provide an axle assembly that is capable of achieving improved assembling efficiency and reducing the size of the axle case as small as possible.
According to the present invention, there is provided an axle assembly that includes an axle case for accommodating right and left driving axles, the axle case forming therein an opening, a differential gear device accommodated within the axle case through the opening of the axle case, a lid connected with the axle case so as to cover the opening, and an input shaft for operatively inputting the driving force from an engine. The differential gear device includes a ring gear and a differential cage. The ring gear has a gear portion formed on a first side surface thereof, which side surface faces the input shaft and is positioned along the axis of the driving axles, for being operatively connected with the input shaft, and forms an axle hole through which an inner end of one of the right and left driving axles relatively rotatably passes. The differential cage is relatively non-rotatably connected with the ring gear via a second side surface of the ring gear, which side surface faces away from the input shaft and positioned along the axis of the driving axles, and forms therein an axle hole through which an inner end of the residual one of the right and left driving axles relatively rotatably passes, so that the inner ends of the right and left driving axles face to each other. The lid includes a first support member for supporting the input shaft and a second support member for supporting the differential gear device. The first and second support members are displaced along the lengthwise direction of the right and left driving axles.
According to the axle assembly having the above arrangement, it is possible to assemble the differential gear device and mount the same to the axle case with improved efficiency, as well as reduce the maximum outer diameter of the differential gear device, thereby achieving downsizing of the axle case.
The second support member may include a first support wall for relatively rotatably supporting the ring gear, and a second support wall spaced apart from the first side wall along the lengthwise direction of the driving axles for relatively rotatably supporting the differential cage. In this arrangement, the second support member is preferably positioned more inwardly than the first support member with respect to a vehicle width direction.
The axle assembly of the present invention may be designed to transmit the driving force to steering driving wheels. According to this arrangement, the axle case has opposite outer ends respectively connected with a pair of steering wheels, which are interlocked with each other through a tie-rod for associated pivoting action. The cover case has an outer surface corresponding to the second support member and provided on the outer surface with an extension member that extends inwardly with respect to a vehicle lengthwise direction. The extension member has a portion with which a fixing end of a power steering cylinder for pivoting one of the pair of steering wheels by pressure is rotatably connected.
According to one embodiment, the differential gear device further includes a pair of side gears accommodated within the differential cage, while being respectively and relatively non-rotatably supported by the inner ends of the right and left driving axles, and a pinion gear accommodated within the differential cage in such a manner as to rotate in meshing engagement with the pair of side gears and move around a rotational axis of the differential cage in association with the rotation of the differential cage.
In the above embodiment, the differential cage may include a flange portion that abuts against the second side surface of the ring gear and forms therein an opening through which the pair of side gears can pass, a body portion extending from the flange portion in a direction away from the ring gear and providing an inner space for accommodating therein the pair of side gears and the pinion gear, and a bearing portion that extends from the body portion in a direction away from the ring gear and forms therein an axle hole through which an inner end of the residual one of the right and left driving axles relatively rotatably passes. The flange portion forms therein at least one hole for receiving at least one fastener for interlocking the differential cage with the ring gear. The body portion forms therein at least one cut-away portion allowing for insertion of the at least one fastener into the at least one hole along the axis thereof.
According to another embodiment, the ring gear has a protrusion axially protruding from the second side surface of the ring gear, and the differential cage forms on a side surface thereof facing the ring gear an engaging hole for receiving the protrusion. The protrusion is engagingly inserted into the engaging hole so that the ring gear and the differential cage are interlocked with each other in such a manner as to be relatively non-rotatable around the axis.